91. Efflorescence is

1. formation of white patches on the surface of bricks due to the presence of insoluble salts in the clay used for making bricks.
2. swelling of bricks due to the presence of carbonaceous matter and gas.
3. deformation arising due to exposure to the weather.
4. presence of impurities in the clay used for making bricks that show up after burning.

92. The strength achieved by a brick depends on

1. composition of brick earth
2. nature of moulding adopted
3. burning and cooling process
4. all the above

93. What is the maximum allowable water absorption (%) of Indian burnt brick of class 2?

1. 5
2. 20
3. 10
4. 15